natwick



1930' A. G. NATWICK ICIRCULATING APPARATUS FOR WOOD PULP DIGESTERS Filed March 17, 1928 BY .{i

I A TORNEY Patented Dec. 9, 1939 PATENT @FFECE ALBERT G. NATWICK, OF ST. CATI-IARINES, ONTARIO, CANADA GIRCULATING APPARATUS FOR WOOD-PULP DIGESTERS Application filed March 17, 1928. Serial No. 262,489.

My invention relates to improvements in devices for reducing, cooking or digesting wood chips in a liquor solution, to pulp, in the paper making industry- The objects of my invention are to promote more complete circulation of the chips and liquor inside the container, digester or cooker, and to bring about acompletely and uniformly cooked pulp, in the shortest time, containing the greatest l0 amount of cellulose, to render the device simple in construction, with the several parts readily accessible for inspection or repair, and generally to adapt the digester to better perform the functions required of it.

I attain these objects by the mechanisms illustrated in the accompanying drawings.

Referring to the drawings, Figure 1 is a vertical longitudinal section of a digester or cooker which contains my improved circulating apparatus.

Figure 2 is an enlarged fragmentary section of the bottom cone ofthe digester showing in detail the lower details of the circulating apparatus.

Figure 3 is an enlarged sectional view showing in detail the nozzle of the circulating apparatus.

Similar letters of reference indicate like parts in the drawing wherein H is the digester casing constructed after the best approved methods, the material of which may vary. The casing H includes the cylindrical body portion 10 having a dome-shaped top 11 provided with an inlet opening 12. The lower end ofthe casing H is provided with a down wardly convergent tapered wall 14, the lower end of which is provided with a pulp outlet opening 15. This wall 14 is of hollow conical formation, and the compartment of the casing H is perfectly elongated from the opening 12 to the opening 15. A is a steampipe passing through the digester' casing by means of a sealing bushing, through which superheated W steam under high pressure passes from steam boiler not shown. The steam passes through steam pipe A to a hollow annular casing or series steam jet B. C is a Venturi pipe which at the top end, has formed therewith a conveying pipe D, and isopen "at'the bottom end. The contents of the digester are drawn up through the bottom end of the Venturi tube by suction caused by the steam issuing from the annular jet B. The jet B comprises a hollow annular casing, providing the central passageway 25 therethrough. Tn cross section the walls are polygonally arranged and provide an annular compartment 27. The steam pipe A connects in the outer wall 29 of the jet casing, so that the steam is fed into the annular compartment 27 from whence it escapes through upwardly inclined duct-s 30 which are arranged in spaced vertical series about the inner wall of the et which defines the passage way 45. The said openings 80 converge upwardly, so that their axes, extended to the vanishing point, are arranged in a conical formation. The purpose of this, is, of course, to provide a conical jet of steam, the apex of which is located at some point in the lower part of the Venturi tube.

The digester casing H is of course vertically supported by means 35. The jet casing B is supported in the lower part of the inverted conical portion 14, by means of downwardly divergent supporting legs 86, of any approved number, which engage at 37 on the inside of the downwardly convergent wall 14 of the casing H, and at their upper ends are pro vided with ri ht angled seats 38 for supporting the jet B axially in the casing H in a horizontal plane.

The Venturi tube C includes upper and lowor tapered or hollow frusto-conical portions and 51, having their smaller ends connected at 52. The respective passageways 54 and 55 therethrough conform to the tapered shape of the said portions. The portion 51 at its larger end is flanged at 56 and is secured to the top wall of the annular et 13 the passageway 25 of the jet B axially aligning and opening into the lower end of the Venturi tube passageway 55; the latter decreasing in size to the constricted throat 52 of the. Venturitube. The upper tube portion 50, of course, has the passageway 54 thereof gradually enlarging upwardly.

The conveyor tube D is formed integral, or is otherwise connected at 60 to the upper end of the Venturi tube, and has the passageway 61 aligning therewith, which is open at the upper end of the tube D; the latter terminating just short of the arcuated dome 11 and having its upper end braced by radial arms (33 which may be connected at ca to the inner surfaces of the side walls of the digester casing H. The action of the fluid in the Venturi tube, whether steam, or pulp, or any other liquid, will be well understood. Since the bore of the tube from the annular jet upwardly is constricted, the velocity of travel therethrough is of course inversely proportional to the area. of the section at different points; the velocity increasing from the jet B to the throat 52, for the obvious purpose of providing an effective circulation. The discharge from the nozzles forms a suction cone on the bottom of the circulating apparatus which draws the contents of the digester into the Venturi tube. As the jets of the steam cone cross at the apex of the first cone, another cone is formed which becomes a pressure cone and which is travelling to the throat of the Venturi tube. A higher velocity is attained at the throat ofthe Venturi' tube. The suction and pressure thus formed by the steam assisted by the Venturi tube carries the contents of the digester into conveying pipe D at the top of which it is discharged and then gravitates to the bottom of the digester when it is again picked up by the suction forces of the suction nozzle at the bottom of the Venturi tube and the process is repeated. The'fiow through the apparatus is continuous as long as steam is allowed to enter the steam ring or jet and positive circulation of the entire contents of the digester is therefore effected.

The material used in the construction of the circulating apparatus may be metal, and this is the case in the sulphate process of digesting wood chips to pulp, since it must of necessity be acid proof. In the sulphate or soda process, a material such as steel or iron or other mate rial not attacked by alkali would be used. The apparatus may vary in height but must be a sufficient height to give complete circulation to the contents of the digester. The size or diameter of the steam line A, Venturi tube and conveying pipe may vary but shall be sufficient to allow the jet B to draw into the Venturi tube and discharge through pipe D a mixture of the entire contents.

' It is understood that the several parts of the foregoingare intended to be assembled and united according to the best process, although all the details of such construction are not illustrated or described. My invention is not limited to the specific form of apparatus shown in the drawings but it is capable of variation iii constructions and shape of its various parts without detracting from its merits as a whole or departing from the scope of the invention. v

I am aware that in the pulp producing digesters, liquor has been circulated throughthe chips by pumps outside the. digester and a steam ejector inside the digester and that a false perforated bottom kept the chips from entering the liquor line.

lVhat I claim is:

1. In a wood pulp digester or cooker of wood pulp or other fibrous materials, the combination of a Venturi tube, and an annular hollow ring-shaped jet discharging at an acute angle into the Venturi tube as a means of increasing velocity and circulating material within the digester orcooker.

2. In a wood pulp digester the combination of a casing, an upright Venturi tube in the casing, and means. for discharging a ringsnaped fluid jet upwardly into the Venturi tube fromthe lower end thereof.

3. In a wood pulp digester the combination of a casing, an upright Venturi'tube in the casing, means for discharging a ringshaped fluid jet upwardly into the Venturi tube from t 1e lower end thereof, and a conveyor pipe at the top of the Venturi tube for receiving circulating materials in an upwar-l flow from the Venturi tube.

i. In a device of the class described a container, an upright tube in the container having a lower open end and an upper end open in the container, and means for forcing a conical jet of circulating fluid forcefully upwardly into the tube from the lower end thereof for drawing materials from the contain'er upwardly into the tube for circulation.

5. In a device of the class described a container, an upright Venturi tube in the container open at its upper and lower ends in the container, and means at the lower end of the Venturi tube and in the container for discharging a conical shaped jet of circulating fluid upwardly into the Venturi tube.

6. In apparatus for treating pulp and the like the combination of a tank, an upright tube in the tank having a passageway there,- thrcugh open at its upper and lower ends in the tank, and means for forcing a jet of steam in conical shaped formation into the lower end of'the tube.

7. In apparatus for treating pulp and the like the combination of a tank, an upright tube in the tank having a passageway therethrough open at its upper andlower ends in the tank, means for forcing a et of steam in conical shaped formation into the lower end of the tube, said tube having the passageway thereof into which the jet of steam is forced gradually restricted upwardly from the base of the jet to the apex of the jet. 7

8. In apparatus for treating pulp and the like the combination of a tank, an upright tube in the tank having a passageway there through open at its upper and lower ends in the tank, means for forcing a jet of steam in conical shaped formation into thelower end of the tube, said tube having the passageway thereof into which the jet of steam is forced gradually restricted upwardly from the base of the jet to the apex thereof, said restriction terminating at a location spaced above the apex of the cone which will be formed by said jet of steam, and the passage way of the tube thereabove gradually enlarging to a predetermined location.

9. In a digester of the class described an upright tank, an upright tube in the tank open at its upper and lower ends in the tank, an annular casing at the lower end of the tube having a central passageway and being hollow to provide a compartment therein surrounding said passageway, the passage way through said last mentioned casing aligning with and facing upwardly into the tube, means for forcing fluid into the ringshaped compartment of said last mentioned casing, said casing having upwardly inclined ducts therethrough to the passageway of the casing, said ducts being relatively convergent to a vanishing point within the tube passageway.

ALBERT G. NATWICK. 

